On the Mating Habits of Peregrine Falcons
by tepid sponge bath
Summary: An unexpected side-effect of an otherwise ordinary case: Sherlock Holmes is deeply fascinated by city-dwelling peregrine falcons.


**Disclaimer**: I lay no claim to the BBC's Sherlock, and I make no monetary profit from this.

**Note: **For katiewont on Tumblr, for Johnlock Challenges' Valentine's Day Exchange. Her prompt was 'Sherlock gets hella into birds'.

**On the Mating Habits of Peregrine Falcons**

"'Strychnine in the Soup_'_?"

John turned in his seat to look at Sherlock, who was – typically enough – passing judgment on the blog over John's shoulder. As the blog concerned him in no small part, John understood, objectively, why he felt he had the right to critique it. Or censor it. Or raise bloody hell when John missed things that he thought were important. But that did not mean that he would sit quietly while Sherlock did it. It was _his _blog after all, and he did think that he had _some_ degree of artistic license.

"That's how she did it, wasn't it?" he said. "Or would you rather 'Rat Poison in the Ratatouille'?"

In reply, Sherlock wrinkled his nose and stabbed one long finger at the laptop screen. "It fits the facts," he conceded. "But that's your title this time? No play on words, no witty references to pop culture? There's not even any suspense, you tell them outright how it was done."

"But not who did it or how you figured it out. And we did know from the outset that it was strychnine poisoning. Besides," John pointed out, "it's just a draft, I'm only laying it out now while it's still fresh before I forget anything." He elected to ignore Sherlock's derisive snort at that. "I can change my mind about it later on, when I've had a bit more time to think."

"And you didn't even mention the bird watching."

"Yes, I did, see? First paragraph, fifth sentence."

"Run-on."

"Still a sentence. If it makes you feel better, I'll do a bit about how we spent the better part of three days stalking all the mating pairs of peregrine falcons in London. I'll even put in how you almost got us hit by a lorry because you got fascinated by one on perched on a television aerial."

"Hm, yes, I can see why that would be amusing to some people." Sherlock's tone indicated exactly what he thought of the people in question. "Irrelevant, though. But I thought you'd like to show how Dodd chose the site for the murder based on her familiarity with the city's peregrines and the gullibility of her victim. The enthusiasm of a new hobbyist knows no bounds."

"I bet he didn't think any harm would come of urban bird watching."

"And look how very wrong he was. Though to be fair not every new hobbyist is a third-rate sous-chef who the management can't get rid of on account of his being the restaurant owner's son…"

"And not every restaurant manager is a bloody fanatical psychopath. But I shouldn't say that in the blog, should I, that wouldn't be nice." John selected a block of text, deleted it, and gave a satisfied sigh (sometimes a bit of judicious editing was all that you needed to achieve, albeit temporarily, a low-grade form of earthly bliss). Then he turned to Sherlock, properly this time. The man had already changed into his pyjamas and assumed the post-case air of inertia and lethargy that made Lestrade despair when there was no getting around the need for Sherlock's participation in his paperwork. You could see it in the slight slump of his shoulders and the way he didn't quite lift his feet when he walked as though taking proper steps expended too much energy. It was, however, also a sign that the last case had been satisfactory, and that it would be a reasonable amount of time (i.e., four days to a week) before he began tearing around the flat, demanding a new one. "You really liked this one," he said, reaching out to put a hand on Sherlock's hip (it was surprisingly nice to be able to do that).

Sherlock shrugged. "It had its merits. Even if the solution was lackluster to say the least."

"Expert bird watcher kills amateur one over misplaced professional concerns, taking advantage of the remoteness of an urban peregrine falcon nest to stage her crime? I thought that was pretty good."

"Unoriginal. Ordinary people commit murder for only so many reasons, and career advancement – or in this case, security – is one of them. And rat poison in the vacuum flask? Hopelessly pedestrian." Sherlock placed his hand over John's, absently, out of habit, and it was wonderful that that was something he did now. "The birds though – I'll admit they were more interesting than I expected them to be."

"That _was _a surprise." John had known that birds were interesting – when he was little, his grandfather used to take him and Harry to see the pair of peregrine falcons that lived on the nearby cliffs if they visited during the right time of year – but he had never associated interesting birds with London. He noticed pigeons and swans in the park and ducks and crows, and never gave them a second thought, and then on a ledge on the building across the street from their rooftop crime scene, there had been a falcon, large as life – a tiercel, resting with his talons held up to his breast feathers, just as he remembered from his childhood, a little dustier perhaps, but that was city life for you. It had been impossible not to point it out to Sherlock, who went on to borrow the dead man's binoculars (much to the consternation of the forensics team), and it was quite possible that that was when he had gotten hooked.

In the days that followed, Sherlock had proven to be remarkably suited to urban bird watching. Even at a distance, he had a keen eye for detail; his knowledge of the city afforded him a good chance at predicting where to find certain kinds of birds once he'd read up on their habits; and, for the right things, he could have remarkable stores of patience. (It also helped that he owned three pairs of binoculars, two of which would have allowed you to count a person's nose hairs from 700 meters.) John had assumed that it was all for the case, but after they'd left the restaurant where Lestrade was making his arrest, instead of heading for home or suggesting that they grab a bite to eat, Sherlock had said that if they hurried, maybe they could spot the peregrines at the Tate Modern again. They had seen them wheeling in the sky in the last light of the evening, and Sherlock, to all appearances, had gone home happy.

"A good one," he said now, slipping into the space between John's knees. "There are very few things that I don't know about this city that are worth knowing, and I didn't think the local ornithology was one of them." He sat himself on John's lap, leaning against the doctor's chest for balance. "I suppose I should thank you for pointing out that falcon on the ledge."

John smiled slowly, moving his hand to Sherlock's waist and tightening his grip (a lap full of Sherlock was a nice thing, but it was also a very full lap, something which the man seemed to forget sometimes, and he had fallen off once or twice). It was typical of Sherlock to say thank-you for that while he'd acknowledged John knocking the meat cleaver out of the suspect's hands with the barest of nods. But then thank-you's were for the little things, like tea and buying the milk and finally removing the pair of lungs from the top shelf of the fridge. The larger, more important things didn't need to be said.

Though they could be acted on.

There was a kiss, long and languid, the sort that could go on forever if you let it. There was Sherlock slipping precariously on John's lap as he tried to do too many things with his hands, and John grabbing two handfuls of arse to keep him from sliding off entirely. There was the progress to the bedroom and the bed when it became clear that the kissing would _not_ go on forever; would, in fact, turn into a different (but related) activity, the preliminaries of which caused the chair to tip and wobble precariously. And there was a slow un-tucking of shirts, an unhurried pulling down of trousers, a blissfully lazy drag of lips against newly exposed skin. It was quite unlike the explosions of clothing and the fierce grabbing and push-pulling that often happened, but it was no less wonderful for that.

It also allowed for more words to be exchanged – conversation, rather than gasped names and expletives, or endearments caught up in heavy exhalations.

"Mating habits," murmured Sherlock contemplatively as he plucked at the waistband of John's pants.

"Yes, that – wait, what?" John lifted his head from the pillow, blinked.

"Peregrine falcons. _Falco peregrinus. _Known to some of our American cousins as duck hawks."

"Oh." By this time, John was used to the things Sherlock could bring up in bed, had on more than one occasion gone over the facts of a case with him like this, and damned if it wasn't one of the sexiest things in the known universe. He lifted his hips off the bed so that the other man could pull his pants off.

"Breeding pairs stay together until one bird dies, and that's a more successful version of monogamy than marriage, don't you think?"

"Hey!" The doctor punctuated his objection by nudging Sherlock's side with his knee.

Sherlock huffed and gave the inside of John's thigh a light nip. "You know I'm right. Monogamy for life isn't inherent to humans: you only have to look at marriage customs across cultures to see that." He planted a thoughtful kiss on the base of John's cock. "But I suppose, occasionally, rarely, very rarely, it's possible for two people to – to bond like they do."

"Hn?" If John was less than articulate, it was because Sherlock had closed his fingers around his prick, had slid back his foreskin, had brought his lips maddeningly close to the exposed glans, and if he could have formed the words, he would have defied anyone to speak in intelligible syllables while that was going on.

"Ultimately. Irrevocably. Possibly with irreversible changes to neural chemistry."

And very little was said after that as Sherlock's mouth became otherwise occupied; as John's world spun and shattered in a burst of white light and white noise; and as he helped Sherlock to a similar state, quite certain that it wasn't just the slip-slide of happy hormones slotting into their cellular receptors that was making him think that Sherlock meant what he thought he did.

"Swans do that too, you know," he said, once he got his breath back. "The mating for life thing. So do love birds." And he giggled before he could stop himself.

"Birds, then," Sherlock conceded, rolling onto his side to face him. "Some kinds of birds. And certain species of vole."

John snorted, and he kissed Sherlock, partly to keep him from going through a list of animals that might have done credit to Noah's ark and mostly because he was at that giddy stage when just watching Sherlock's lips move did _things_ to him. Sherlock, bless him, didn't seem to mind at all – he seemed to like it very much, actually, even if it didn't quite succeed in distracting him from his train of thought.

"We haven't seen the peregrines at the Battersea Power Station yet," he said delicately, when they were nose to nose, making it clear that this was an unacceptable state of affairs and that something needed to be done about it, immediately if possible.

"'The enthusiasm of a new hobbyist knows no bounds?'" John prodded him in the ribs.

Sherlock hummed in acquiescence, caught John's hand and brought it to his lips. "It's better than Cluedo. I'd even rate it higher than Dimmock's jewel thief. Even he should have figured out by now that the necklace is in a safe deposit box under Nora Sylvius's father's middle name spelled backwards."

"Will you tell him that?"

"Mmmm, no. Not unless he asks."

"You're just being contrary," John smiled. "All right, Battersea then. We can go tomorrow."


End file.
